An ultrasonic sensor that sends ultrasonic waves and receives ultrasonic waves reflected on an obstacle detects, for example, the presence of obstacle based on the wave reflected on the obstacle, and also detects a distance to the obstacle based on a time from sending ultrasonic waves to receiving reflected waves.
FIG. 12 is a sectional view of conventional ultrasonic sensor 502 disclosed in PTL 1. Ultrasonic sensor 502 is mounted on a target device 503, such as a bumper of vehicle, for use.
Ultrasonic sensor 502 shown in FIG. 12 is mounted to target device 503 by being held with fastening device 501 to be fastened to target device 503. Aperture 530 for exposing exposure surface 710 through which ultrasonic waves of ultrasonic sensor 502 mainly enter and exit is provided in target device 503. Dimensions and shapes of ultrasonic sensor 502 and fastening device 501 are designed such that a surface of target device 503 opposite to a surface on which fastening member 501 is fastened (e.g., an outer surface of the bumper) is substantially flush with exposure surface 710.
In above fastening device 501, when double-sided adhesive tape 610 is used for fastening onto target device 503, double-sided adhesive tape 610 is previously attached to one surface of fastening member 1 (hereafter referred to as “adhesive surface”), and fastening device 501 is bonded to target device 503 by pushing double-sided adhesive tape 610 against target device 503.
However, when double-sided adhesive tape 610 is used as described above, fastening device 501 may be fastened at a position deviated from a position where fastening device 501 is to be fastened if double-sided adhesive tape 610 contacts target device 503 at the deviated position.
FIG. 13 is a front view of conventional fastening device 601 disclosed in PTL 2. As shown in FIG. 13, protrusion 691 is provided on fastening device 601 to contact target device 503 before double-sided adhesive tape 610, thereby preventing double-sided adhesive tape from contacting target device 503.
With the above structure, protrusion 691 contacts target device 503 so as to prevent double-sided adhesive tape 610 from contacting target device 503, and to finely adjust a position of fastening device 601, thereby improving workability.